JPH01171805A - Manufacture of ceramic molding - Google Patents

Abstract

PURPOSE:To reduce the occurrence of cuts, cracks and the like due to gas generation, by granulating a ceramic material powder body, adding an organic binder thereto, regulating a mud slurry and casting it in a mold, calcining it tentatively at a specified temperature as occasion demands after the molding is dried, and then calcining the molding obtained in an isostatic press. CONSTITUTION:Globular granulates of 10-1000mum in grain size are obtained, for example from a ceramic material powder body by a spray dry and granulating method. A mud slurry is conditioned by adding an organic binder thereto and casted into a mold made of resin and others. The obtained molding is dried and tentatively calcined at 600-800 deg.C as occasion demands. Next, the molding is coated with latex, etc., and dried to cover its whole surface and pressed isostatically at pressures of hundreds to thousands kg/cm<2>. By calcining the pressed molding with a normal method, the vaporization of water from the molding becomes easy because the space between particles is relatively large due to granulates used in molding.

Description

[Detailed description of the invention] [Industrial application field] The present invention is a ceramic molded product! ! Regarding the method of sending.

[Prior art]

In recent years, ceramic molded products made from fine ceramic powder have attracted attention for their superior mechanical, chemical, and thermal properties compared to molded products made of metal or organic materials, and are being used in a variety of fields. development is underway.

Therefore, in order to improve the mechanical and thermal properties of a ceramic molded product, a sintered body with a homogeneous, dense, and fine crystal structure is required. It is necessary that the ceramic raw material be fine, and accordingly, the ceramic raw material is required to be made into a finer powder.

On the other hand, one of the traditional methods for molding ceramics is the slurry immersion molding method, and this molding method is suitable for molding large-sized, complex-structured ceramic moldings, and its importance is being reaffirmed. ” [Problem to be solved by the invention] As described above, it is necessary to finely powder the ceramic raw material in order to improve the mechanical and thermal properties of ceramic molded products, but it is necessary to finely powder the ceramic raw materials. The finer the ceramic raw material is, the more difficult it is to mold it. Particularly in the slurry casting method, the finer the ceramic raw material, the more difficult it is to obtain a relatively uniform molded product with few internal defects, which causes the following problems. arise.

(a) Generally, in the slurry casting method, organic binders (deflocculants, binders, etc.) and water are added to ceramic powder to form slurry, and this slurry is placed in a casting mold made of gypsum, resin, etc. The slurry is molded by being inserted into the molded body, and the slurry is subjected to pretreatment such as deaeration in order to prevent the occurrence of internal defects such as pores in the molded product prior to being inserted into the molded product. However, even if the compact formed by this method is dried and fired, properties such as bulk density and strength are not sufficiently expressed, especially when compared with a sintered compact obtained by press forming. The properties of the sintered body obtained by cast molding are lower by 5 to 20%. The cause of this property deterioration is that when water in the slurry is absorbed into the casting mold during casting molding and solidifies as a molded object, and when moisture existing between raw material particles is scattered during the drying process, inside the molded object. This is presumed to be because fine pores remain as internal defects.

(b) In the slurry immersion molding method, when the molded product is released from the mold and dried, the molded product is likely to break due to shrinkage, etc., and damage such as cracks can easily occur. The density tends to be non-uniform, and due to the difference in density, the solidification of the molded product and the shrinkage rate during drying are different, which tends to cause damage such as breakage and cracks.

(e) Molded bodies containing II are often calcined when a large amount of organic binder is used, but in this case, when the added organic binder burns and generates gas, the molded body may be cut, causing damage such as cracks. Likely to happen. In particular, this tendency becomes stronger as the ceramic raw material becomes finer.

Therefore, an object of the present invention is to establish a method for producing ceramic molded articles with excellent mechanical and thermal properties even if they are large and have a complicated structure.

[Means to solve the problem]

The first object of the present invention is a method for manufacturing a ceramic molded article comprising the following steps (a) to (e).

(b) Process of granulating raw material powder for ceramics.

(b) A step of adjusting the slurry by adding an organic binder to the granules obtained in the granulation step.

(c) Sludge? I4g Step of loading the slurry obtained on I4 into a mold.

(d) A step of drying the molded product obtained in the step including II and subjecting it to an isostatic press.

(e) A process of firing the molded body obtained in the isostatic pressing process.

Furthermore, the present invention is a manufacturing method in which the molded product obtained in the bonding step is dried, then calcined, and subjected to isostatic pressing.

In the granulation step (a) of the present invention, the following known methods can be employed as the granulation method. That is, (1
) Spinal granulation method in which humidified powder is given rolling action to agglomerate into spherical particles, (2) Granules are made by compressing a certain amount of raw powder into a certain size and shape. Compression granulation method, (
3) FDS is a process in which powder is fluidized and a liquid is sprayed onto it from a spray nozzle to coat the particle surface with liquid and granulate it.
NyiL grain method, (4) the slurry is passed through a pressurized nozzle or 2
Injection granulation method, which obtains spherical granules by pulverizing the powder using a fluid nozzle and air-cooling it in a granulation tower, (5) Spray drying granulation method, which slurries raw material powder, spray-dries it, and granulates it at the same time. can be adopted.

Among these granulation methods, the spray drying granulation method and the fluidized Ma granulation method are preferable.Although the shape of the granules is not particularly limited, it is preferably spherical, and the average particle size is 10 to 10.
1000μ ugly, especially preferably 20 to 100μ ugly.
If the average particle size is less than 10 μm, the time for inlaying during inlay molding will be longer, internal solidification will be slow and a uniform molded product will not be obtained, and moisture will scatter during drying and calcination. The dispersion of the generated soot will be insufficient. On the other hand, the average particle diameter is 10
If it exceeds 00μ-, it is 7F of slurry! 4 adjustment is difficult,
Casting cannot be performed.

In the slurry adjustment step (b), the slurry is adjusted by adding an organic binder using the granules described above, and in the casting step (c), the slurry is constantly poured into a casting mold made of gypsum, street fat, etc. It is cast under pressure or pressure, and when it reaches the desired thickness, it is released from the mold at the end of the process to obtain a molded product. Subjected to static press.

In the isostatic pressing step (d), prior to pressing, latex or the like is applied to the entire surface of the molded product and dried to cover the entire surface, resulting in a weight of several 100 to several 1000 kg/
The pressed compact is subjected to an isostatic press at a pressure of c+a'' and is fired in the final firing step (e) by a conventional method, and the firing conditions are appropriately selected depending on the desired characteristics.

[Action/effect of the invention]

According to this manufacturing method, since granules are used as the ceramic raw material, the plasticity of the cast molded product is increased, and even if the molded product is complex and has different wall thicknesses, it will not cause unattached internal parts or separation. There is little occurrence of damage such as cuts during molding, and because the gaps between particles in the molded body are relatively large, the moisture inside the molded body is easily evaporated and scattered during drying, and the amount of shrinkage due to moisture evaporation and scattering is small. Therefore, there is less damage such as cuts and cracks to the molded product during drying.

The soaked compact is placed in an isostatic press and equiaxially pressed from the entire surface, resulting in a strong bond.The sintered ceramic compact obtained by firing this compact has excellent mechanical and thermal properties. Become something.

Even in molded bodies that require calcination, the gaps between particles within the molded body are relatively large, so the gas generated by combustion of the organic binder is likely to scatter, resulting in cuts, cracks, etc. caused by the generation of soot. There is also less damage.

[Example 1] Raw material powder containing 2IIlt% of clay-based sintering aid, average particle diameter of 0.4μ theory, 0.8μ^1□Os, 3mo
1% Y2O.

Zr with an average particle diameter of 0.4 μm + 0.81 J m including
A granulated powder with an average particle diameter of 80 μm is obtained using a total of 41a of 0z by (1) spray drying granulation method, (2) fluidized bed granulation method, and (3) compression granulation method. In the granulation methods (1) and (2), an organic binder (carboxylic acid-based Pine Gu 1
In the granulation method (3), each raw material is packed in ice packs using a special granulation device (wt%, wax 0.5wt%).
The powder is subjected to isostatic press (CIP) at a pressure of 000 Kg/am", then crushed and classified with a sieve to obtain a granulated powder. For comparison, (4) ungranulated powder is also used. .

For slurry adjustment, organic binder (carboxylic acid-based Pine Gu0.
01-0.9wt%, acrylic acid-based pine goo 0.01
~0.9wt%) and antifoam agent Q, using Q5wt%,
Each granulated powder is mixed and dispersed in a kneader to form a slurry, and the ungranulated powder is mixed and dispersed in a bottle mill to form a slurry. Mixing and dispersing granulated powder in a bot mill is undesirable because the granulated powder may be destroyed, and mixing and dispersing ungranulated powder in a kneader makes it difficult to mix uniformly.

The test mold for casting is shown in Fig. 1(a) and consists of an upper mold 1 and a lower mold 2.
Pressure casting is carried out at a pressure of 100.degree. C., and drying of the obtained cast body is started under constant temperature and humidity conditions of a temperature of 80° C. or lower and a humidity of 60% or higher, and the humidity is gradually lowered to dry.

After drying, latex is applied to the molded body, dried, the entire surface is covered with a rubber film, and then subjected to CIP at a pressure of 2000 Kg/Cm2.The molded body subjected to CIP is fired at 1400°C, and the first A ceramic molded article 10 having the shape and dimensions shown in Figure (b) is obtained. Samples of the center portion 11 and the outer peripheral portion 12 were cut out from the molded product 10, and the bending strength of the samples before and after heat treatment was measured using the JISRIGOI four-point bending test method. The results are shown in Table 1, and
The bending strength value of the sample obtained by the press molding method is shown as the judgment criterion.The heat treatment was performed in an autoclave at 25
The heat treatment time was 500 hours for ^120 degrees and 250 hours for ZrO.

Referring to the same table, when using granulated powder, the strength before and after heat treatment is higher than when using ungranulated powder (and regarding the granulation method, when spray drying granulation method is used) The same strength as that of a press-formed product can be obtained.As for CIP, although it is an ungranulated powder, there is a considerable difference in strength depending on the presence or absence of CIP, and the entire surface is firmly compressed by CIP. It can be seen that the strength is improved when the average particle size of the raw material powder is 0.8μ.
It can be seen that the strength of 0.4μ Tsuru is higher than that of 1.

(The following is a blank space) [Example 2] Using the slurry prepared in Example 1, Figure 2 (,), (b)
A pump impeller 20 having the shape and dimensions shown in Fig. 3 (
A ceramic molded body with a large and complicated structure such as a butterfly valve body 30 having the shape and dimensions shown in a) and (b) was formed by pressure casting and drying, and the embedding ability was evaluated. . Performance evaluation is based on the appearance of each molded object during the molding and drying process.
The results are shown in Table 2. Damaged areas 21 to 24 are the damaged areas of the impeller 20 shown in Figure tIIJ2, and damaged areas 31 and 32 are the damaged areas of the impeller 20 shown in Figure tIIJ2.
This is the damaged part of the valve body 30 shown in the figure.

The casting ability is determined by the raw powder type M (^1205, Zr0z
), but there are differences depending on whether or not granulation is used and the granulation method. As for the granulation method, spray drying granulation method and fluidized bed granulation method are suitable, and compression granulation method also uses an average particle size of 0.8 as the raw material powder.
Good results are obtained when μm is used. When ungranulated powder was used, drying and shrinkage occurred from the inked surface layer before the ink was sufficiently attached to the center of the molding, and some of the ink also collapsed even after being released from the mold halfway. This can be seen in Example 1
Although it is possible to perform casting test molds using ungranulated powder, the manufacturing method of the present invention is not suitable for casting molded bodies with complex structures, large sizes, and large differences in wall thickness. This means that it is extremely effective.

(Margin below) Table 2

[Brief explanation of the drawing]

Figure 1 (,) is a longitudinal cross-sectional view of the casting test mold, Figure (b) is a side view of a ceramic molded product using the same test mold in casting, and Figure 2 (,) is casting molding. and a plan view of one molded body (pump impeller) formed by drying, FIG. 3(b) is a longitudinal cross-sectional view of the same molded body, and FIG. The plan view and the figure (b) are a side view of the same molded object. Explanation of symbols 10...Molded product, 20...Pump impeller, 3
0...Butterfly valve body.

Claims (2)

[Claims] (1) A method for producing a ceramic molded article comprising the following steps (a) to (e). (a) Process of granulating raw material powder for ceramics. (b) A step of adjusting the slurry by adding an organic binder to the granules obtained in the granulation step. (c) A process of casting the slurry obtained in the slurry preparation process into a mold. (d) A process of drying the molded body obtained in the casting process and subjecting it to an isostatic press. (e) A process of firing the molded body obtained in the isostatic pressing process. (2) The manufacturing method according to item 1, wherein the molded body obtained in the casting step is dried, then calcined, and subjected to an isostatic press.